Thanks Dan for the reply. I have looked at several different field guides
and many photos and I can see what you mean about the shape of the throat
patch. I generally never paid much attention to it except to note the
color. I guess if someday the species is split then we will have hybrids
rather than intergrades.
Ken Trease

On Thu, May 26, 2022 at 4:11 PM Dan McDougall-Treacy <danmcdt at gmail.com>
wrote:


> Ken, one way I distinguish the Audubon and Myrtle forms is by the shape of

> the throat patch, an approach that is helpful throughout the year. I think

> of the Myrtle showing the throat patch flaring out and upward toward the

> auricular area, and the Audubon throat patch more vertically aimed toward

> the breast or underwing coverts.

> Recently I observed a bird with a bright white throat patch (Myrtle-y),

> and in the shape of the Audubon throat patch.

>

> The National Geographic field guide also shows the Myrtle with a whitish

> supercilium,though that field mark might not always be visible.

> Your photos show yellow/white in the (Audubon-shaped) throat patch,

> suggesting an intergrade condition. And one of those birds has a distinct

> white supercillium

> Others may know of different distinguishing field marks. Birds of the

> World goes into a number of subtleties.

>

> Dan McDougall-Treacy

>

> On Thu, May 26, 2022 at 3:15 PM Kenneth Trease <krtrease at gmail.com> wrote:

>

>> I recently returned from a trip to south-central Oregon. I photographed

>> two different Yellow-rumped Warblers (YRWA) that I thought might be

>> intergrades as they seem to have some characteristics of both Audubon's and

>> Myrtle forms. I would be interested to hear other's opinions-intergrades

>> or just within the normal variation for this species? Here is a link to

>> the photos on Flickr:

>>

>> https://www.flickr.com/photos/cavuken/albums/72177720299278430

>>

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>